Modular heat exchanger housing

ABSTRACT

The specification discloses an air-to-air, polymeric heat exchanger having a housing and a core removably mounted within the housing. The housing includes four generally indentical duct units, which are secured to one another, and a top and a bottom, which are secured to the duct units. The core includes a pair of end walls and a plurality of tubes extending between, and opening through, the end walls. Each end wall includes a plurality of tubular projections or pockets extending from the end wall in a common direction. Opposite ends of the tubes are secured within the tubular pockets in the opposite end walls. A method of constructing the core includes the step of severing the tubular projections after the tubes are positioned therein to expose the tube interiors through the end walls. Preferably, the tubular projections are severed using a hot wire to also fuse the tubes within the end walls.

This is a division of application Ser. No. 800,662, filed Nov. 22, 1985,now U.S. Pat. No. 4,735,261 which is a division of application Ser. No.417,639, filed Sept. 13, 1982, now U.S. Pat. No. 4,588,543, issued May13, 1986.

BACKGROUND OF THE INVENTION

The present invention relates to heat exchangers, and more particularlyair-to-air heat exchangers.

It is often desirable to transfer the heat from a relatively warm airmass to a relatively cool air mass. It is also often desirable toprevent the two masses of air from intermixing during such transfer,such as where one of the masses is relatively dirty or contaminated. Avariety of air-to-air heat exchangers has been developed for conveyingtwo air masses past one another to effect the heat transfer. Often theheat exchangers include a housing and a core unit removably mountedwithin the housing. The core may be periodically removed from thehousing and cleaned as necessary to keep the heat transferring surfacesclean. Preferably, both the housing and the removable core arefabricated of plastic or polymeric materials to reduce corrosionproblems associated with contaminated air masses flowing through theexchanger.

However, known heat exchangers are not without their drawbacks. Firstly,the housings are typically specialized constructions requiring arelatively large number of parts. Accordingly, assembly costs are highbecause the manufacturer must make and inventory all of these parts forassembly of the units. Additionally, a large stock of replacement partsmust be maintained for subsequent servicing of the units.

Secondly, the core units of the heat exchangers are also difficult andexpensive to manufacture. Although heat exchanger cores have been madeof plastic, known methods of assembling these cores are time-consumingand expensive. In one construction, the adjacent tubes within the coreunit are fused together under heat and pressure. An example of thismethod of construction may be seen in U.S. Pat. No. 3,616,022, entitledMETHOD OF MAKING HEAT EXCHANGE COMPONENTS and issued Oct. 26, 1971, toWithers; and U.S. Pat. No. 3,537,935, entitled APPARATUS FORMANUFACTURING A HEAT EXCHANGER COMPONENT FORMED WITH FLEXIBLE PLASTICTUBES and issued Nov. 3, 1970, to Withers. This method of assembly mustbe carefully controlled at the proper temperature and pressure toprevent spoiling the core unit during manufacture. Additionally, themethod restricts air flow between and around the heat transfer tubes. Inanother construction, the tubes are fused to one another by insertinghot mandrels into adjacent tubes to soften and expand the tubes intofusing engagement with one another. An example of this construction maybe seen in U.S. Pat. No. 2,433,546, entitled METHOD AND APPARATUS FORFORMING PLASTIC RADIATOR CORES and issued Dec. 30, 1947, to Cornelius.However, in this method also, the temperature of the mandrels must bevery carefully controlled to prevent excessive or inadequate softeningof the ends of the heat exchange tubes during the fusing operation. Ifnot carefully controlled, the tubes of the core are excessively orinadequately fused. Proper alignment of tube ends, one with the others,is also difficult in known manufacturing methods. Additionally, althoughit is desirable to use dissimilar materials (e.g., Teflon, nylon,polyethylene, polypropylene, and most crystalline polymers) infabricating separate elements of the core unit to maximize anticorrosiveproperties while minimizing cost, suitable adhesives for such dissimilarmaterials are expensive or simply unavailable; and consequently suchdissimilar materials cannot be used.

SUMMARY OF THE INVENTION

The aforementioned problems are solved by the present invention.Essentially, a heat exchanger is provided including a housingconstructed from modular, generally identical duct units which interfitwith one another to define the core chamber. Accordingly, the number ofparts required to assemble the housing is greatly reduced over knownheat exchangers, reducing both the initial cost of manufacture of theunit and subsequent inventorying of replacement parts.

Further, the heat exchanger includes a core comprising first and secondend walls and a plurality of tubes extending between and communicatingthrough the end walls. Each of the end walls includes a plurality oftubular projections, or pockets, extending from the end wall in a commondirection. Opposite ends of the tubes are secured within the pockets inthe end walls. Consequently, the core is extremely strong and durable,and yet may be constructed relatively easily and inexpensively.

Additionally, the present invention includes a preferred method forforming the core of the heat exchanger including the steps of providingan end plate defining a plurality of pockets extending in a commondirection from the end plate, inserting a heat exchange tube into eachone of the pockets in the end plate, and severing the pockets to exposethe interior of the tubes through the end plates. Accordingly, thepresent core is more readily and inexpensively manufactured than coreunits currently available on the market. Additionally, the methodgreatly reduces the possibility of spoilage during manufacture of thecore unit. Preferably, the end plate and the heat exchange tubes areboth fabricated of fusible materials, and the pockets are severed usinga hot element to also fuse the tubes in the end wall. In such case,virtually any thermoplastic, or even dissimilar thermoplastics, can beused in core fabrication.

These and other objects, advantages, and features of the invention willbe more readily understood and appreciated by reference to the writtenspecification and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, exploded view of the heat exchanger of thepresent invention;

FIG. 2 is a sectional view of the assembled heat exchanger taken alongplane II--II in FIG. 1;

FIG. 3 is a fragmentary, enlarged view of the area within circle III inFIG. 2;

FIG. 4 is a fragmentary, enlarged view of the area within circle IV inFIG. 2;

FIG. 5 is a sectional view of the assembled heat exchanger taken alongplane V--V in FIG. 1;

FIG. 6 is a fragmentary, enlarged view of the area within circle VI inFIG. 5;

FIG. 7 is a fragmentary, perspective view of a core end plate with heatexchange tubes inserted therein prior to removal of the end platepockets; and

FIG. 8 is a sectional view taken along plane VIII--VIII in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A heat exchanger constructed in accordance with a preferred embodimentof the invention is illustrated in the drawings and generally designated10. The exchanger includes housing 12 (FIGS. 1, 2, and 5), defining acore-receiving chamber 14 (FIG. 2), and core 16 (FIGS. 1, 2, and 5)slidably mounted therein. Housing 12 comprises four identical duct units18, top 20 permanently secured to the duct units, and a bottom 22releasably secured to the duct units. Core 16 is slidably receivedwithin housing 12 through the lower end of the housing with bottom 22removed therefrom. Core 16 comprises a pair of end plates 24 and aplurality of heat exchanger tubes 26 extending between, andcommunicating through, the end plates. End plates 24 are dimensioned toclosely interfit within chamber 14 (FIGS. 2 and 5) such that a mass ofair traveling through heat exchanger 10 through duct 18a to duct 18cmust pass through tubes 26 and a mass of air passing through duct 18b to18d must pass over and around tubes 26.

Heat exchanger 10 effects an air-to-air heat exchange, particularlywhere one of the air masses is dirty or contaminated. One suchenvironment is a poultry confinement area, where the air to be exhaustedfrom the confinement area contains suspended dust, feathers, and otherparticulate and/or corrosive matter. Housing 12 is suspended from theceiling of the poultry confinement area on chains 28, each of whichincludes S-hook 30 releasably secured in the housing. Warm exhaust airis forced through core 16 and more particularly through tubes 26 bymoving the air through duct 18a to duct 18c. The make-up air (i.e., theambient air outside the poultry confinement area) is forced past core16, and more particularly over and around tubes 26 by moving the airthrough duct 18b to duct 18d. Core 16 is releasably maintained withinhousing 12 on bottom 22. Periodically, as necessary, core 16 is removedfrom housing 12, by releasing bottom 22 from the remainder of thehousing and lowering both the core and the bottom. Core 16 is thencleaned, for example by hosing off heat exchange tubes 26 so that anyparticulate matter collected therein is washed away. Core 16 is thenreplaced within housing 12 and bottom 22 secured to ducts 18 so that theunit is again operational.

Turning more specifically to the construction of housing 12, duct units18 (FIGS. 1, 2, and 5) each include a funneled portion 32 and acylindrical connecting portion 34 leading therefrom. Ducts 18a, 18b,18c, and 18d are generally identical to one another; consequently, onlyduct 18a will be described in detail. Connecting portion 34 isdimensioned to receive flexible duct (not shown) or other apparatussuitable to convey an air mass to or from heat exchanger 10. Funnelportion 32 flares outwardly from connecting portion 34 and terminates inupper flange 36a (FIGS. 5 and 6), right flange 36b (FIGS. 2 and 4),lower flange 36c (FIG. 5), and left flange 36d (FIGS. 2 and 3). All offlanges 36 together define a generally rectangular end to funnel portion32.

Upper flange 36a (FIGS. 5 and 6) extends upwardly from funnel portion 32and is oriented generally perpendicularly to the axis of connectingportion 34. Lower flange 36c is generally identical to and coplanar withupper flange 36a however extending from funnel 32 in a directionopposite to the upper flange. Flanges 36a and 36c provide an attachmentsurface for top 20 and bottom 22 as will be described.

Right side flange 36b (FIGS. 2 and 4) has a dogleg cross sectioncomprising lateral portion 37 extending from funnel 32, offset portion38 extending from the lateral portion, and securing portion 40 extendingfrom the offset portion. Lateral portion 37 and securing portion 40 aregenerally perpendicular to the axis of connecting portion 34 and alsogenerally perpendicular to offset portion 38. Left side flange 36d(FIGS. 2 and 3) is generally L-shaped in cross section including lateralportion 42 oriented generally perpendicularly to the axis of connectingportion 34, and securing portion 44 oriented generally perpendicularlyto the lateral portion.

As illustrated in FIGS. 3 and 4, adjacent duct units are securedtogether by overlying securing portion 44 of left side flange 36d of oneduct over securing portion 40 of right side flange 36b of an adjacentduct. The two overlying portions 40 and 44 may be secured together usingany combination of adhesive 46, screws 48, or rivets (not shown). Toconstruct a complete housing 12, four ducts 18 are interconnectedresulting in the configuration shown in FIG. 2. For purposes ofdescription only, duct 18a will be denominated the exhaust air inletduct; duct 18b the make-up air inlet duct; duct 18c the exhaust airoutlet duct; and duct 18d the make-up air outlet duct. Compressive seals50, such as neoprene, are secured to the inner surfaces of side flanges36b and 36d (FIGS. 3 and 4) of duct units 18a and 18c to seal core 16against housing 12 as will be described. All of ducts 18, as well as top20 and bottom 22 are fabricated of a thermoplastic material, such asABS, approximately one-eighth inch thick.

Top 20 and bottom 22 (FIGS. 1 and 5) are generally identical to oneanother; consequently, only top 20 will be described in detail. Top 20includes a generally square body 51; hub 52, formed in the center of top20, and eight ribs 54 extending from hub 52 to the perimeter of thecover. Peripheral channel 56 (FIGS. 1 and 6) is formed about the entireperimeter of top 20. Channel 56 is generally U-shaped in cross section(FIG. 6) comprising a first flange 58 extending upwardly and generallyperpendicularly from body 51, a bight portion 60 extending generallyperpendicularly outwardly from flange 58, and outer flange 62 extendinggenerally perpendicularly downwardly from bight portion 60. The width ofchannel 56 is selected such that top flange 36a and end plate 24 fitside-by-side within the channel. Upper flange 36a is permanently securedto outer flange 62 using any combination of adhesive, screws 64, orrivets (not shown), for example as used to interconnect duct units 18.

Bottom 22 (FIGS. 1 and 5) additionally defines five drain holes 66through which condensate within chamber 14 can exit. One of holes 66 islocated in hub 52 and the others are located one each in the center ofeach side of the bottom. Latches 68 (FIG. 5) extending between each ofducts 18 and bottom 22 releasably secure the bottom to the ducts. Thelatches may be any type commercially available for releasably securingone object to another. Lower flanges 36c of ducts 18 and end plates 24are received within perimeter channel 56 of bottom 22 (similar to FIG.6) when the bottom is secured to the duct units.

Core 16 (FIGS. 1, 2, and 5) includes end plates 24a and 24b and aplurality of heat exchange tubes 26 extending therebetween. End plates24 and tubes 26 are fabricated from a thermoplastic material, such asABS, with the plates being approximately one-eighth inch thick. Each oftubes 26 is approximately one-half inch in diameter and includes a wallwhich is approximately three to five, and preferably four, mils thick.This wall thickness has been selected as providing the requisitestrength for core 16 while permitting the desired heat transfer betweenthe air within and without tubes 26. The tubes are secured to andcommunicate through both of end plates 24. Additionally, tubes 26 arearranged into alternate horizontal offset rows designated 70 and 72(FIG. 1) along the height of core 16. The center-to-center distancealong a horizontal line between any two adjacent tubes is approximatelyone and one-quarter inches. The center-to-center distance along avertical line between any pair of tubes both in alternate rows 70 or 72is approximately three-quarters inch. Accordingly, the vertical distancebetween the center lines of adjacent rows 70 and 72 is approximatelythree-eighths inch.

As illustrated in FIGS. 7 and 8, core 16 of the present invention isconstructed in accordance with a novel method. Prior to assembly of core16, each of end plates 24 has a honeycombed configuration, including agenerally planar body portion 74 and a plurality of pockets 76 extendingfrom a common side thereof. Each of pockets 76 includes a generallycylindrical side wall 78 integrally joined to body 74 and a bottom wall80 (FIG. 8). Accordingly, each of pockets 76 defines an open end 82generally coplanar with body 74 and a closed, or abutment, end 84 whichserves as an abutment surface for tubes 26.

Core 16 is constructed by inserting end 86 of one of tubes 26 into eachof pockets 76 in end wall 24a. Preferably, tubes 26 are fully insertedinto pocket 76 so that tube end 86 abuts surface 84 of bottom wall 80.After one of tubes 26 has been so inserted into each of pockets 76, thepockets and tubes located therein are severed, or cut, for example alongline 88 to expose the interiors of tubes 26 through end plate 24. Iftubes 26 and end plates 24 are fabricated of fusible materials, forexample those plastics that cannot be easily bonded together with anadhesive, the cut along line 88 may be made with a hot wire. As the wirepasses through pockets 76, the pockets are severed, and each of tubes 26is fused with its associated pocket to fuse, or fasten, the tubes withinend plate 24. Consequently, dissimilar and hard-to-bond materials can bejoined to form a high-strength core. Alternatively, a saw may be used tosever pockets 76; in such case it is preferable to include an adhesivebetween tube ends 86 and pockets 76 to insure the proper securement ofthe tubes within the pockets. Tubes 26 can be attached to end plate 24aby dipping the end plate into a suitable adhesive (e.g., solvent cement,thermosetting/chemically curing adhesives) and positioning the tubes inpockets 76. Opposite end wall 24b is secured to tubes 26 in an analogousmanner.

End plates 24 are selected to extend the full width between side flanges36b and 36d (FIG. 2) and the full height between top and bottom flanges36a and 36c (FIG. 5). Consequently, end plate 24a (FIG. 2) is sealedabout the entire periphery of exhaust air inlet duct 18a. Similarly, endplate 24b is sealed about the entire periphery of exhaust air outletduct 18c.

Assembly and Operation

Housing 12 is fabricated by first permanently securing four duct units18 together (FIG. 2) to define core-receiving chamber 14. Top 20 is thenpermanently secured to ducts 18. Latches 68 are installed on ducts 18and bottom 22 so that the bottom may be releasably secured to theremainder of housing 12.

Core 16 is fabricated and inserted into housing 12 through the openingexposed when bottom 22 is removed from the housing. Typically, core 16is placed on bottom 22 which is then raised into position, raising thecore into core-receiving chamber 14. Latches 68 are secured after bottom22 is fully seated to secure core 16 within chamber 14. Heat exchanger10 is suspended from the ceiling of the poultry house on chains 28 withS-hooks 30 inserted through receiving holes in housing 12. Appropriateair handling equipment, such as flexible ducts, fans, and filters, arethen connected to each of connecting portions 34 of duct units 18.

Air handling equipment is connected so that the contaminated exhaust airis forced through exchanger 10 from duct 18a to duct 18c so that the airmust pass through tubes 26. The make-up air to be heated or cooled isforced through exchanger 10 from duct 18b to 18d. As the two masses ofair are conveyed through the duct, the heat from the warm air istransferred to the cool air through tubes 26. The turbulance created inthe make-up air as the air must pass around and over the tubes enhancesthe heat transfer. The extent of the heat transfer is determined by thematerial of which tubes 26 is constructed, the thickness of the walls ofthe tubes, the dimensions of the tubes, and the configuration of thetubes for creating turbulance. As the exhaust air is conveyed throughexchanger 10, the particulate matter suspended therein will be depositedinside tubes 26. Consequently, it will be necessary to periodicallyremove core 16 from housing 12 for cleaning. This is easily accomplishedby unlatching latches 68 and lowering bottom 22 and core 16 restingthereon out of the remainder of housing 12. Core 16, particularly tubes26, may then be hosed off or otherwise cleaned and then reinstalledwithin housing 12 for further heat exchanger operation. Optionally, core16 may be secured, for example using adhesive, to bottom 22 to preventaccidental sliding of the core from the bottom during removal orinstallation of the core.

It should be understood that the above descriptions are intended to bethree preferred embodiments of the invention. Various changes andalterations might be made without departing from the spirit and broaderaspect of the invention as set forth in the appended claims, which areto be interpreted in accordance with the principles of patent law,including the doctrine of equivalents.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A heat exchanger housing comprising four duct units grouped into first and second sets, each said set including an inlet duct unit and an outlet duct unit through which a quantity of fluid flows into and out of said heat exchanger housing, all said duct units being substantially identical to one another and of a single piece unitary construction, each of said duct units having opposite sides, each said side being directly connected to a side of an adjacent duct unit of the other set so that said duct units collectively define a core-receiving chamber, said inlet duct unit and said outlet duct unit of each set being further arranged to define a path through which the quantity of fluid flows as it passes through said heat exchanger housing, each said duct unit further including a first structure defining an inner opening and a second structure defining an outer opening, said inner and outer openings cooperating to form a path through which said quantity of fluid flows as it passes through said duct unit, and said first and second structures of each duct unit defining openings which are oriented substantially parallel to each other.
 2. A heat exchanger comprising:a first inlet duct unit; a first outlet duct unit; a second inlet duct unit; a second outlet duct unit, all of said duct units being substantially identical to one another and of a single piece unitary construction, each of said duct units including:a first flange structure, a second flange structure overlapped with and secured to the first flange structure of an adjacent duct unit, a top flange structure, and a bottom flange structure; a top member secured to all of said top flange structures; a bottom member mounted on all of said bottom flange structures, said duct units and said top and bottom members together defining a core-receiving chamber; and a core including a pair of end plates and a plurality of tubes extending therebetween, each said tube having a pair of opposite open ends, said ends being positioned to open beyond the end plates; said first flange structure, said second flange structure, said top flange structure and said bottom flange structure of each of said duct units cooperatively forming a substantially continuous peripheral rim; and said first inlet duct unit and said first outlet duct unit being positioned in opposing relation with one another such that said peripheral rims thereof define abutments which engage said end plates of said core to hold said core against shifting longitudinally.
 3. A heat exchanger as defined in claim 2 wherein at least one of said top and bottom members is releasably mounted on said duct units to facilitate access to said core-receiving chamber.
 4. A heat exchanger as defined in claim 2 wherein said bottom member defines a drain hole through which liquid within said core-receiving chamber may exit. 